I am going to make a WAG here is say the RV doors are probably made by Lippert and they specify the locks that are used in their doors. You might try calling them and asking if they manufacture a lock that is a suitable replacement.
You might also try contacting Bauer and ask them if they have a retrofit for the Trimark lock. Bauer is the company that made the keypad lock on my Accolade and they have been willing to assist when I had an issue with the lock.
Also, why not measure the bolt and latch positions for the lock on the side of the door (face plate). You might be able to cut the lock opening larger for a keypad lock if the bolt and latch are in the same position. That positioning might be standard across the industry (operative word is might).
As to why Thor uses Trimark, it's probably because they got a good deal on Trimark locks and people buy the rigs as configured with those locks. It could also be the locks come with the doors. BTW, Thor is not the only manufacturer that uses Trimark locks on their motorhomes. Triamark was the lock used on my Forest River SunSeeker a number of years ago.
US Army (Ret)
2020 Entegra Accolade 37TS
2019 Jeep Grand Cherokee Trailhawk (Toad)
FMCA - F432054